There are known aircraft undercarriage legs including a strut assembly articulated to the structure of the aircraft and receiving a sliding rod equipped in its lower portion with an axle that carries the wheels of the undercarriage leg. Some undercarriage legs include an orientation control for orienting the wheels of the undercarriage leg. These orientation controls include a member mounted to turn on the strut assembly (such as a collar, or a rotating tube) that is connected to the sliding rod by a torque link allowing free sliding of the rod but constraining the sliding rod to rotate with the rotating member. The angular position of the latter relative to the strut assembly is determined by an orientation actuator.
On some aircraft, such as the Airbus A320 for example, the orientation actuator includes a rack that is mounted to slide in cylinders on either side of the strut assembly and meshes with a toothed portion of the rotating member forming a pinion. The rack may be moved hydraulically, as on the A320, or by means of a linear electromechanical actuator as proposed in the documents EP 2 620 673 and EP 2 527 689.
These orientation controls are subject to high deformations at the level of the meshing engagement between the pinion and the rack, which makes the use of a recirculating ball screw type transmission difficult, given the stiffness of this kind of actuation.